Dosing gun, in particular high-pressure dosing gun

ABSTRACT

A dosing gun (500) comprising a revolving valve element (518), arranged fixedly in a first casing (506) which is immovably connected with the gun housing (502). The first casing (506) has a second spring-loaded casing (544) linked to it in a mobile way, which contains a hollow cylinder (514) having on its frontal part valve seats (542, 554). The dosing gun (500) can operate with or without a supply of compressed air.

The invention relates to a dosing gun, in particular a high-pressuredosing gun for spraying a medium such as polishing paste.

In patent DE-C-22 04 942, a high-pressure dosing gun is described forthe first time in which a pressure determining the motion of the valvebody such as a valve piston is generated by a compressed air motor in asupply chamber containing the medium to be sprayed, such as polishingpaste. To do so, the medium encloses the valve piston at least in thearea of the valve seat, such that the valve piston is at a distance fromor in contact with the valve seat depending on the prevailing pressure,in order to thereby spray or retain the medium as required.

When the medium is sprayed without the supply of air, this is referredto as the "airless" method. Before the medium can be sprayed, it isnecessary to bleed the high-pressure dosing gun. To do so, separatevalves are necessary in some cases or the air present is ejected too atthe start of spraying, with the result that there is no reproducibleoutput of the medium at this time.

German patent DE-A-32 02 189 describes a high-pressure dosing gun inwhich the valve body is arranged fixedly and the spring-pressure-loadednozzle containing the valve seat can be in contact with or at a distancefrom the valve piston. The spring surrounds the nozzle coaxially and isfixed by a cap nut. A design of this type has proved to have majordrawbacks. A further drawback of this gun design is that the sealingaction is between the valve body and a section of a cylinder elementcontaining the nozzle, said section being movable relative to the valveelement, so that a relatively large sealing area is obtained from whichhigh forces result, which in their turn must be compensated or balancedby a spring element with correspondingly high force. The result is therisk that even with minor leaks from the valve seat or from the sealitself an internal pressure can build up which is no longer sufficientto move the cylinder element. It is of major importance, particularlywhen using or operating with abrasive media such as polishing paste, forthe valve arrangement to be sufficiently open, since otherwise aself-destructive effect as a result of uneven washing out at the valveseat or valve shank will occur in spite of the use of carbides orsimilar, thereby further accelerating wear. In addition, the manualopening necessary for putting into service the valve arrangement forbleeding the system is only possible with an additional special tool.The sensitivity necessary for operating an arrangement of this type withatomizer air is inadequate for achieving the consistent high level ofdosability required. This is not achievable with the device shown inDE-A-32 02 189.

High-pressure dosing guns of this type have the further drawback thatfrequent changing is necessary of wear parts such as the valve body orvalve element containing the valve seat, such as the perforated disk. Inaddition, design drawbacks may then be present if the valve body isdesigned as a hollow needle through which flows the medium to besprayed.

The object of the present invention is, among others, to develop adosing gun such that replaceability of the wear parts is reduced, andhigh reproducibility of the sprayed media is achieved by simple designmeans, where small sealing surfaces must be selected in particular forbetter control of the forces generated. In addition, simple replacementof any worn parts should be possible. Finally, it should also bepossible to operate the dosing gun with the "airless" method or with acompressed air supply as required. A further object of the presentinvention is to achieve bleeding with simple means, with both rapidbleeding and if necessary continuous bleeding being possible. Inaddition, the nozzle should be adjustable with simple means without theneed for cap nuts or similar that have to be tightened.

The invention is particularly noteworthy in that the valve body ismounted detachable from a first casing combining with it to form a unit,in that the first casing extends from the cartridge element or thehousing, and in that the valve seat is provided in the frontal part of ahollow cylinder which is movable relative to the first casing and whichforms a unit with a second casing movable against the spring element andopposite the first casing. Here, the valve body in particular can beflowed around by the medium and is supported against the first casing byspacer elements, which in their turn are an integral part of the valvebody. In particular, it is provided that the valve body with the spacerelements is designed symmetrical with regard both to the main axis andto the secondary axis. The same applies with regard to the hollowcylinder containing the valve seat.

The second casing holding the hollow cylinder has one or more leakholes, which firstly prevent medium penetrating between the hollowcylinder and the first casing from collecting and impairing themovability of the arrangement, and secondly showing that inspection ofthe seal and of the hollow cylinder/valve seat is necessary.

The last-named features in particular have the advantage that the wearparts revolve to allow double the use in comparison with known devices.In other words, a revolving valve body and a revolving hollow cylinderare provided whose frontal parts each have a valve seat. The firstworking chamber containing the medium and situated between valve seatand valve body is sealed on the outside of the hollow cylinder,preferably using a grooved ring. Consequently, only a small sealingsurface is necessary, so that the forces generated can be bettercontrolled.

In an embodiment, a second working chamber between radially runningsections of the first and second casings is designed such that whencompressed air is admitted it can be moved against the force of thespring element, with a connection being in existence between the workingchamber and the outlet channels in the area of the nozzle. In otherwords, the dosing gun in accordance with the invention can be operatedboth in the "airless method" and with compressed air supplied.

The hollow cylinder containing the valve seats has on its front a nylonseal tapering outwards in some areas, that can be applied to the innerface of the nozzle. A suitably designed section of the second casing isadjusted to the external geometry of the nylon seal, and a cap nuttightening the nozzle in the direction of the seal can be screwed on tothe outside of said casing. This ensures firm positioning of the hollowcylinder with seal and nozzle relative to the second casing, whichsurrounds the first casing in some areas and is movable along it.

The second casing is in its turn surrounded by a further cap nutextending from the cartridge element or housing. The spring elementapplying pressure to the second casing in the direction of the housingruns in the area between the second cap nut and the outside of thesecond casing. A stop is provided preferably in the front end of thesecond cap nut to limit the axial movement of the second casing andhence of the valve seat away from the housing or valve body.

In a dosing gun in which the valve body is designed movable against theforce of a spring element relative to the cartridge element or housing,the invention proposes that the nozzle is held by the cap nut so as tobe rotatable and axially movable against the force of the springelement. In addition, a disk element holding the valve seat is designedto be in floating contact with the nozzle.

The theory according to the invention permits the generation, by meansof a tool such as a conventional screwdriver, of a lever effect betweenthe cap nut to be designated as nozzle nut and the nozzle itself, thiseffect moving the lever into the interior of the high-pressure dosinggun. As a result, the air in the lines of the device and in connectedhose lines is allowed to escape. As soon as the tool is removed, thevalve arrangement closes automatically, i.e. the valve body is again upagainst the valve seat, so that an adequate sealing effect is achieved.

In a further embodiment, the first cap nut holding the nozzle isfastened to a further cap nut that screws to the cartridge element ordosing gun housing, and the front orifice of the further cap nut facingthe first cap is matched to the diameter of the contact collar of thenozzle. This part is designed slightly projecting beyond the adjacentsection of the second cap nut, so that on the inside the valve elementsuch as the perforated disk can contact it. The resultant advantage isthat when the nozzle is removed, i.e. when the first cap nut isunscrewed, the valve body remains in contact with the valve seat, sothat adequate sealing against uncontrolled spraying of the medium isensured since the valve disk is held by the front section of the secondcap nut.

The valve body itself is preferably movably mounted in a valve pistonguide having an internal replaceable wear bush interacting with thevalve body.

The sealing effect in the first working chamber containing the mediumand situated between the valve seat and the valve body is achieved by anall-round seal provided in the area of the wear bush in the wall of thevalve body. Here too, only a small sealing surface is needed, so thatsensitive opening and closing of the nozzle is ensured.

Substantial parts of the valve arrangement such as valve body, valvepiston guide, wear bush and a spring plate interacting with the springelement are only fitted. All parts are easily removed and replaced oncethe second cap nut has been removed. This facilitates maintenance of thedosing gun.

In addition to the possibility in accordance with the invention ofsimple nozzle adjustment, it must also be noted that the airless nozzlesusually used do not spray a round jet in most cases, but a fan-type one.In this case, therefore, the nozzle must be aligned radially. In knowndevices, the nozzle is tightened at its fastening collar with the aid ofa cap nut, which as a rule must itself be held with a separate wrench tostop it turning as well. Using the theory according to the invention,these expensive measures are no longer necessary, since the force of thespring element acts right through the spring plate, the valve piston andthe valve seat to the contact collar of the nozzle, and the nozzle is insealing contact with the wall of the cap nut facing it. The nozzle canbe turned to any required position, using for example an open-jaw wrenchengaging in a wrench surface provided on the nozzle without the need toloosen beforehand and subsequently retighten the cap nut.

In order to operate a dosing gun with and without compressed air supply,the valve body is surrounded at least in sections by a hollow guidecylinder, the valve body and the hollow guide cylinder are movablerelative to one another, a valve element containing the valve seat isfixed between the hollow guide cylinder and the nozzle, and a furtherworking chamber is arranged between the hollow guide cylinder and anelement connected thereto and an element holding the valve body orextending therefrom, said working chamber being acted upon by compressedair for adjustment of the valve body relative to the valve element, thefurther working chamber being connected to the air outlet channels inthe area of the nozzle.

With the dosing gun in accordance with the invention, it is possible toperform various spraying and dosing processes as required withoutalteration of the basic structure. The dosing gun is suitable foraggressive, abrasive, low-viscosity and high-viscosity materials. Thefurther working chamber is or is not connected to a compressed airsource depending on the type of spray operation selected The integralparts of the dosing gun are simple in design and therefore economicallyproducible. the entire dosing gun strips down quickly and easily,meaning that wear parts subjected to heavy wear from abrasive materialscan be replaced quickly and easily.

The invention is described in more detail in the following on the basisof preferred embodiments shown in the drawings, in which furtherdetails, advantages and features are shown.

FIG. 1 shows a first embodiment of a dosing gun shown in perspective,

FIG. 2 shows the dosing gun according to FIG. 1 in side view, partiallyin longitudinal section,

FIG. 3 shows a second embodiment of a dosing gun,

FIG. 4 shows a third embodiment of a dosing gun with axially movablevalve body,

FIG. 5 shows a particularly noteworthy embodiment of a dosing gun,

FIG. 6 shows the dosing gun according to FIG. 5, but with compressed airsupply,

FIG. 7 shows in detail a check valve,

FIG. 8 shows in detail a valve arrangement intended for a dosing gun,and

FIG. 9 shows a particularly noteworthy embodiment of a valve arrangementin the form of a revolving element.

FIGS. 1 and 2 show a dosing gun (1) for spraying of liquid or pastymaterial, i.e. materials having different viscosities. The dosing gun(1) contains a housing (2) with whose one side a compressed-air pistoncylinder arrangement (3) is connected. On the opposite side of thehousing (2), a valve arrangement (4) is provided. On another side of thehousing, a check valve (5) is attached. A shut-off cock (6) is connectedto the check valve (5) and has a connection (7) for a hose not shown indetail and leading to a source for the pressurized spray material. Thecompressed-air piston cylinder arrangement (3) contains a hollowcylinder (8) closed on one side by a sealed disk (9) and fastened by acap nut (10) to the cylinder (8).

A connection for a hose not shown in detail is fastened in the disk orcover (9) and is connected via a control valve, in particular athree-way valve, also not shown in detail, to a compressed air sourcefor low pressure in particular. In the middle of the disk (9), a stopspindle (12) is arranged having an adjusting nut (13), disposed outsidethe compressed-air piston cylinder arrangement (3), with which the axialinsertion depth of the stop spindle (12) in the interior of the cylinder(8), hereafter referred to as hollow cylinder (8), can be adjusted.

The shut-off cock (6) has an actuating handle not shown in detail. Inthe housing (2) is a threaded hole (14) for screwing in a furtherconnection not shown in detail which is connected via a hose also notshown in detail to the mentioned compressed air source or to a furthersource.

A hollow threaded spigot (15) of the check valve (5) is screwed into atapped hole not designated in detail of the housing (2). This tappedhole tapers at that end arranged in the housing (2) and is connected viaan orifice (16) to a cylindrical cavity (17) extending through thehousing and having at its ends sections of larger diameter notdesignated in detail. One of these sections located on that side of thecavity (17) facing away from the compressed-air piston cylinderarrangement (3) has a female thread. Into this female thread is screweda cartridge-type insert (18) which has a section (19) projecting intothe cavity (17) in which a cylindrical supply chamber (20) is arrangedthat is connected via a passage (21) in the section (19) to a free space(22) in the cavity (17). The orifice (16) opens into the free space(22).

A rod (23) is arranged in a longitudinally movable manner in the supplychamber (20), and its end facing away from the supply chamber (20) isheld in a piston (24) mounted movably in the interior of the hollowcylinder (8). A seal (25) is arranged in the cylindrical wall, notdesignated in detail, of the piston (23). The piston (24), the innerwall of the hollow cylinder (8) and the disk (9) surround a workingchamber (26) which is accessible to gases via the connection (11).

The hollow cylinder (8) is closed off at its end facing away from thedisk (9) with a circular flange (28) inserted into the cylindricalcavity and fastened with a lock ring (27), said flange having a passageorifice not designated in detail for the rod (23). The flange (28)contains holes not designated in detail disposed parallel to thelongitudinal axis of the hollow cylinder (8), into which holes thescrews (29) are inserted that are screwed into the tapped holes of thehousing (2). The flange (28) and the housing (2) are both provided withaligned leakage holes not designated in detail. Furthermore, bleed holesnot designated in detail are provided.

The cylindrical supply chamber (20) tapers at one end to a tapped holeon the same axis, not designated in detail, into which is screwed ahollow needle (30), also designated as the valve body, having an endsection (31) provided with a male thread. The hollow needle (30), whichhas a central channel (32) running in the longitudinal direction,belongs to the valve arrangement (4). At the outlet of the channel (32)into the supply chamber (20), a closing seal (33) is inserted into arecess. The hollow needle (30) contains a central section (34) providedwith an integrally cast nut head, adjacent to which section is thesecond end section (35) having cylindrical form, the outside of which isdesigned at least partially as a guide surface (36).

The insert (18) projects with one section (37) beyond the housing (2).In the inside of the section (37) is a hollow cylinder (38) which formsa guide surface for a section (39) of a sliding element (40). A seal(41) is arranged in the wall of the cylinder (38). The sliding element(40) tapers radially in steps towards the section (39), thereby creatinga free space between the wall of the cylinder (38) and the slidingelement (40). A coil spring (42) is inserted in this free space, one endof which is supported by the ring-shaped wall of the step on section(39). The other end of the coil spring (42) is supported in a cap nut(43) screwed onto a male thread of section (37) and having a centralpassage for that part of the sliding element (40) projecting beyond thesection (37). The sliding element (40) is provided in its interior witha cavity (44) in which is located the central section (34). The wallfacing the housing (2) of section (39) forms together with the walls ofthe cylinder (38) a further working chamber connected via a channel (46)in the insert (18) to the tapped hole (14). In section (19), a seal (47)is provided that seals the channel (46) and the working chamber (45)against the space (22) in which the material to be sprayed is located.The cavity (44) tapers to a cylindrical guide surface (48), i.e. to aso-called hollow guide cylinder, which surrounds the guide surface (36)on the valve body (30). A seal (49) is arranged in the guide surface ofthe hollow guide cylinder (48).

The channel (32) is angled outwards radially in the vicinity of that endof the hollow needle (30) projecting from the housing (2) and has anoutlet into a cavity (51) formed by a cylindrical recess in the slidingelement (40). The diameter of this cavity (51) is greater than thediameter of the hollow guide cylinder (48). The cavity (51) extends tothe front (52) of the sliding element (40).

A valve plate (53) closing the front orifice of the cavity (51) andhaving a central passage orifice (54) contacts the front end (52). Theedge of this passage orifice (54) is designed as a valve seat surfacefor a valve head (55) located at that end of the valve body (30) orhollow needle that projects from the housing (2). The valve head (55)can be an integral part of the hollow needle (30). It is also possibleto attach a separate valve head (55) to the end of the hollow needle(30). The valve head (55) is preferably of spherical or hemisphericaldesign.

The sliding element (40) is provided at its end facing away from thehousing (2) with a male thread not designated in detail and onto whichis screwed a cap nut (56) that presses an insert (57) with a nozzle (58)against the valve plate (53) and the latter against the front face (52).

The insert (57) contains in addition to the nozzle (58) air outletchannels (59) running to an annular cavity (60) arranged between theinner face of the insert (57), the cap nut (56), the valve plate (53)and the front face (52). The annular cavity (60) is connected via achannel (61) to the cavity (44).

Above the check valve (5) is a nut-type screw union (63) at thedeflection point of the material conveying channel leading to theshut-off cock (6). In a continuation (64) of the screw union (63) is apressure sensor, not designated in detail, that has an optical displayelement (65) for pressure. If necessary, electrical pickup and, forexample, digital display of the pressure is possible.

A further pressure sensor (62) is connected with a sensor element in theinterior to the supply chamber (20). The pressure readings can beelectronically evaluated and used to monitor the function of the entiresystem.

As regards FIG. 2, it may be noted in addition that the hydraulic unitcomprising the cartridge and the valve arrangement is separable from thecompressed-air motor by a grooved ring (123), thereby permitting easiermaintenance.

Six different spraying methods are feasible with the device describedabove, and are described in detail in the following.

1. For continuous spraying of a material, the insert (57) described ingreater detail in conjunction with FIG. 2 is used. The tapped hole (14)is connected to the compressed air source via a three-way valve notshown in greater detail. The working chamber (26) is connected toatmospheric air pressure via the connection (11). Compressed air passesthrough the tapped hole (14) and the channel (46) to reach the workingchamber (45). From there, the compressed air flows via the cavity (44)and channel (61) to the annular cavity (60) from which it escapes viathe air outlet channels (59) surrounding the nozzle (58) at regularintervals. The annular end facing the working chamber (45) of section(39) has been designed sufficiently large to match the air quantitycoming from the air outlet channels such that the pressure building upin the working chamber (45) is sufficient to move the sliding element(40) against the force of the coil spring (42) by a small amount, e.g. 2mm. As a result the valve plate (53) is lifted off the valve body (55).A passage is obtained at the valve containing the valve plate (53) andvalve body (55). The sprayed material is conveyed under pressure to thesupply chamber (20) and flows from there through the channel (32) intothe cavity (51). Spray material therefore passes continuously throughthe orifice of the valve to the nozzle (58) from which the medium comesout and passes to the range affected by the compressed air coming fromthe air outlet channels (59) and forming together with the medium anair/material mix which can be applied under pressure as a spray mistonto an object.

2. It is also possible with the dosing gun (1) shown in FIGS. 1 and 2 tospray a viscous material having a precisely preset volume determined bythe axial position of the stop spindle (12). A scale not shown in detailon the adjusting nut (13) displays the volume of the supply chamber (20)that can be set using the stop spindle (12). The connection (11) isconnected to the compressed air source using, for example, a three-wayvalve in the same way as for the tapped hole in order to achieve theaforementioned method. Under the pressure with which the spray materialis conveyed, the supply chamber fills up with the material until thepiston (24) is up against the stop spindle (12). A spring for retractingthe piston (24) to its one limit position is therefore unnecessary. Theworking chambers (26) and (45) are then supplied with compressed airthat spreads evenly to working chambers (26) and (45). The valvearrangement (4) operates in the same way as already described. Thepiston (26) slides the rod (23) into the supply chamber (20), as aresult of which a pressure builds up in this chamber by which the checkvalve (5) is closed. Therefore no further material is fed into thesupply chamber (20). The rod (23) displaces the viscous material presentin the supply chamber (20), and the material flows via the channel (32)and the valve to the nozzle (58) until the front face of the rod (23) isup against the closing seal (33). The working chambers (26) and (45) arethen subjected to atmospheric air pressure. As a result, the valvearrangement (4) closes and the check valve (5) opens. Material againpasses under pressure via an annular chamber (67) in the supply chamberwall to the front of the rod (23), which is forced out of the supplychamber (20) by the material flowing into the latter until the piston(24) contacts the stop spindle (12). The sequence described above canthen be repeated.

The compressed air supply to the working chamber (26) can be reduced byan air intake butterfly valve not shown in detail, to allow the pressurein the working chamber (26) to become just high enough for the checkvalve (5) to close and the rod (23) to move to the closing seal (33).

3. Continuous spraying at low pressure without compressed air supplyusing the material conveying pressure (mottling) is based on theassumption that no air outlet channels (59) are present. A correspondinginsert without air outlet channels (59) is installed in the gun (1), forexample. It is also possible to provide a seal in the annular cavity(60) by which the air outlet channels (59) are sealed. The compressedair passes into the working chamber (45) and moves the sliding element(40) into the valve opening position against the force of the coilspring (42). Material can now pass from the supply chamber (20) via thechannel (32) and the cavity (51) to the open valve, from which it passesover into the nozzle (58). The material quantity leaving the nozzle perunit of time depends on the pressure in the supply chamber (20) or thematerial conveying pressure. The duration of spraying is preferablycontrolled by a time-lag relay with which the supply of compressed airto the working chamber (45) is interrupted, as a result of which thevalve arrangement (4) closes.

4. Volume dosing during spraying at low pressure without compressed airsupply using the material conveying pressure (mottling) is achieved whenthe working chamber (26) is supplied with compressed air in the same wayas described in item 2. In order not to generate too high a pressure inthe working chamber (26), the air supply is restricted when the presetmaterial quantity is forced out of the supply chamber (20).

5. For high-pressure spraying of the material without compressed airsupply, the working chamber (45) is subjected to atmospheric pressure.

The working chamber (26) is connected to compressed air by a controlvalve not shown. The pressure in the working chamber (26) allows thepiston (24) to move the rod (23) into the supply chamber (20), in whicha pressure is thereby generated that closes the check valve (5). Afurther movement of the rod (23) leads to an increase in pressure in thesupply chamber (20), the channel (32) and the cavity (51) until thepressure acting on the valve plate (53) exceeds the spring pretension.As a result, the sliding element (40) is slid into the opening positionof the valve arrangement (4). The material coming out of the valvepasses to the nozzle (58) and leaves the latter at high pressure,whereby it is atomized. As long as high pressure is present in thematerial, the valve arrangement (4) remains open. When the piston (20)meets the flange (28), the pressure drops rapidly so that the valvearrangement (4) closes. The high pressure necessary for airlessatomization is generated by the piston (24), which has a larger workingsurface than the rod (23).

6. Under certain conditions, it is necessary to exercise a furthereffect on high-pressure (airless) atomization by adding compressed airwithin certain limits. This process is called the airless method withair assistance. In this method, the working chambers (26) and (45) aresimultaneously acted upon by compressed air. The insert (57) againcontains air outlet channels (59) in addition to the nozzle (58).However, a butterfly valve is arranged between the tapped hole (14) andthe compressed air source. Initially, the compressed air supply to theworking chamber (45) is, for example, without pressure or closed. Whenthe compressed air supply to the working chamber (26) is released, apressure builds up in the supply chamber (20) that continues in themanner described in item 5 up to the cavity (51) and opens the valvearrangement (4). It is then possible for compressed air to be suppliedvia the working chamber (45) by opening the butterfly valve to thecavity (44) and the channel (61), and to the annular cavity (60) and theinsert (57), this compressed air being supplied with the atomizedmaterial. A spray mist is thereby affected in the manner required. Thefurther the butterfly valve is opened, the less air and pressure isavailable for the working chamber (26), so that the high pressuregenerated by the piston (24) can be reduced parallel thereto. Thepressure present in the expansion area also drops, and the valvearrangement (4) could close if necessary, which is however compensatedby the compressed air affecting the sliding element (40) via the workingchamber (45) and building up sufficient pressure to keep the valvearrangement (4) open.

The stroke of the rod (23) ends at the seal (33) and is set to arequired value by the stop spindle (12) as in the dosing methoddescribed under 2. and 4.

FIG. 3 shows, in purely diagrammatic form and partly in section, part ofa further embodiment of a dosing gun, in particular a high-pressuredosing gun (200), having a cartridge element (209) detachably insertableinto a gun element (212). The gun element (212) contains a compressedair motor not shown, for example of the type described above, in orderto generate a pressure of the required quantity by movement of a rodmovable inside a supply chamber holding the spray material. The spraymaterial, such as polishing paste, extends in the drawing in thedash-lined area up to a valve head (213) of a valve body such as a valvepiston (205). The valve piston (205) is arranged axially movable in avalve piston guide (207) enclosing a wear bush (20) and along which thevalve piston (205) is movable. The sealing action between the valvepiston (205) and the wear bush (206) is achieved by a seal (215) placedin a groove (214). The wear bush forms, together with its rear annularend wall (216) a stop for a spring plate (208) of which the rear endwall (217) interacts with the valve piston (205). The spring plate(208), which is opened in the direction of the gun element (212), holdsa compression spring (211) that rests on a cover (210) that is fixedsubstantially immovable by contact with, for example, a stop not shownwhen the dosing gun (200) is assembled. The cover (210) has a U-shapedsection, and the continuous edge (218) extending in the direction of thespring plate (208) is sealed off from the valve piston guide (207) ofhollow cylinder form. The force exerted by the spring (211) perceptiblyeffects a movement of the spring plate (208) and hence of the valvepiston (205) in the direction of a nozzle (202) which is held by a firstcap nut or nozzle nut (201). The nozzle nut (201) is in its turn screwedto a second cap nut (204) which surrounds some areas of the outside ofthe cartridge element (209). The sealing action between the cap nut(204) and the cartridge element (208) is achieved via a staticallyacting O-ring seal (219).

The nozzle (202) has a contact collar (220) resting against the innerface of the first cap nut (201). A valve element such as a perforateddisk (203) containing a valve seat (222) is mounted in floating fashionbetween the valve head (213) of the valve piston (205) and the contactcollar (202).

The valve piston (205) can be lifted off the valve seat (203) againstthe force exerted by the spring (211) depending on the pressureprevailing in the area of the valve head (213) generated by thecompressed air motor and transmitted via the spray material. Thispermits spraying of the medium by the nozzle (202).

The front part of the second cap nut (204) has a section (223) extendingradially inwards whose clear diameter is greater than that of thecontact collar (220), but smaller than that of the perforated disk(203).

The mode of operation of the features in accordance with the inventionof the high-pressure dosing gun (200) is as follows.

The nozzle (202) held by the first cap nut or nozzle nut (201) can bepressed against the perforated disc (203) by means of a screwdriverinsertable into a recess (221) provided in the nozzle nut (201), as aresult of which the nozzle (202) is moved inwards. The floating-mountedperforated disk (203) containing the valve seat (222) and in contactwith the nozzle (202), including the valve piston (205), is therebymoved against the force of the closing spring (211). The lifting of thecontact collar (220) of the nozzle (202) from the inner face of thenozzle nut (201) ends the sealing action on the inner face of the nozzlenut (201), so that the air in the valve arrangement can escape past thenozzle jacket. When the tool is removed from the recess (221), the valvearrangement closes automatically, since the force of the spring (211)has the effect that the spring plate (208), via the valve piston (205)and the valve seat (202) or perforated disk (203), exerts a force on thecontact collar (220) for sealing contact with the cap nut (201).

If continuous bleeding is required, the cap nut (204) is loosened fromthe cartridge element (209) until the spring plate (208) is in contactwith the stop (216) of the wear bush (206). If the cap nut (204) isfurther unscrewed, the spring force can no longer act on the valvepiston (205), so that the closing force of the valve piston (205) orvalve head (213) at the valve seat (222) is neutralized and hence anyair can escape through the perforated disk (203) and the nozzle.

If the nozzle nut (201) is now removed with the nozzle (202) forreplacement, the interior of the dosing gun (200) remains sealed, i.e.can remain under pressure. The cause of this is that the perforated disk(203) is still in contact with the inner face of the section (223)projecting radially inwards of the second cap nut (204). As a result,the valve head (213) is tight against the valve seat (222) and seals theinner cavity.

FIG. 4 shows further particularly noteworthy embodiments of theinvention. The same reference numbers have generally been taken forelements already shown in FIGS. 1 and 2.

From the housing (2) projects a hollow cylinder section (70) extendingin the direction of the valve arrangement (4). The hollow cylindersection (70) can here also be an end section of a cartridge (100)projecting from the housing (2), said cartridge being detachablyarranged in the housing (2) but remaining stationary relative to thehousing (2) when the spraying unit is operated. Housing (2) andcartridge (100) can also be designed as a unit. A piston (101) isdesigned to be movable inside the hollow cylinder section (70). Thepiston (101) of the embodiment according to FIG. 4 represents a sectionof the valve body (101) designed movable relative to the hollow guidecylinder (48). The valve body (102) is substantially designed as a longhollow cylinder which in its turn surrounds a hollow needle (103) firmlyscrewable to the cartridge (100) or housing (2) and opening to thesupply chamber (20). The hollow needle (103) also designated as hollowspigot is provided in the supply chamber with the seal (33) to which thedisplacement piston (23) can be applied at maximum stroke. The spraymaterial can now be forced through the spigot (103) in order to flow viaa radial orifice (104) into the cavity (51) between the hollow guidecylinder (48) and the outside of the valve body (102). Depending on theprevailing pressure there, the valve head (55) then lifts off from thevalve seat (53). The orifice (104) therefore represents the connectionbetween the chamber (105) and the cavity (101), the former being limitedby the inner wall of the valve body (102) and the front face of thespigot (103).

The hollow guide cylinder (48) in its turn is held by a hollow cylinder(73) screwable onto the housing hollow cylinder section (70). Thepot-shaped end section (83) of the valve arrangement (4) and a furthercap nut (112) with pressure regulation effect are in turn screwable ontothe hollow cylinder (73).

Between the wall (106) facing the piston (101) of the hollow cylinder(73) holding the hollow guide cylinder (48) and in its turn firmlyconnected to the hollow cylinder section (70) of the cartridge (100) orhousing (2), and the valve-side front face (107) of the piston (103),the further working chamber (78) is provided that is connectable via thechannel (79) to the compressed air connection (80), in order to move thepiston (101) against the force of the spring (76) depending on theprevailing pressure, and thereby lift the valve body (102) from thevalve seat (53). Channels (107) and (109) extend from the workingchamber (78) and open into the air outlet channels (59). It is possiblein accordance with the embodiment in FIG. 4 for the air outlet channels(59) for spraying the medium coming out of the nozzle (58) to runbetween the pot-shaped end section (83) and a centering cap (110) whichin its turn holds the nozzle (58). Furthermore, a truncated-cone-shapedseal (111) preferably of polymer is located between the nozzle (58) andthe valve seat (53).

By adjusting the regulating ring (112), the connection between thechannels (108) and (109) can be altered so that more or less compressedair is emitted via the air outlet channels (59).

The movement of the sliding element (102), which according to theinvention provides a rigid unit with the piston (101) movable againstthe spring (76) exerting a force directed away from the housing (2), cantake place exclusively and/or assisted with compressed air.

FIG. 8 shows a preferred embodiment of the guide cylinder (48), alsodesignated as wear bush, with the material nozzle (58) held by it. Thematerial nozzle (58) can thus be inserted into the guide cylinder (48)from the housing side, with centering being assured by projecting noses(120) and (122). The material nozzle itself has a carbide insert (124)that forms the actual nozzle and projects with a flat face (126) on thehousing side beyond the holding element (125) holding the nozzle. Thisflat face (126) doubles as a valve seat for the valve head (127) on thefront face of the valve body (102) or (30). An elastic element whichthen acts as the valve head (55) can then be placed in the front face ofthe valve body (30), (102), to compensate for any tilting. It ispossible by appropriate design to achieve a simple construction andhence easy maintenance of the valve head, the valve plates (53)described in connection with FIG. 2 then being unnecessary. It is alsonot necessary for the valve head to be designed spherical, as shown inFIGS. 2 and 4. Instead, the surface facing the valve seat (126) can bedesigned flat, as indicated in FIG. 6.

FIG. 7 is an exploded view of the check valve (5) which can be designedas a replaceable unit in accordance with a further feature of theinvention. The check valve (5) comprises a screw-in cage (174) in whichis arranged a contact pressure spring (176) with carbide or ceramicsealing sphere (178), valve seat (180) and sealing disk (182). When thecheck valve (5) is worn, the previously mentioned unit comprisingelements (174) to (182) only needs to be removed from the housing forreplacement by a new one. The result is considerably easier maintenance.

FIGS. 5 and 6 show particularly noteworthy embodiments of high-pressuredosing guns (500) and (600) in accordance with the invention thatoperate with or without compressed air (airless method). In all otherrespects, the design of the high-pressure dosing guns (500) and (600) isidentical, so that identical elements are numbered identically.

A cartridge (504) is arranged fixedly in a gun housing (502). A firstcylindrical casing or bush (506) is screwed into the cartridge (504) andhas a radial outward projection (508). The front end (510) of the casing(506), i.e. of the hollow-cylinder-type body, has an internally pointingradial section for holding a grooved-ring seal (512) between the firstcasing (506) and a hollow cylinder element (514). A so-called revolvingvalve body (518) comprising a cylinder section (520) with sphericalvalve sections (522) or (524) at the front faces is clamped detachablybetween the grooved-ring seal (512) and a section (516) extendingradially inwards of the cartridge element (504). The section (520) canbe designed hollow. Spacer elements project from the outside of thesection (520) in the direction of the inside of the first casing (40),in order to ensure a fixed position of the revolving valve body (518) inthe casing (506). These spacer elements are numbered (526) and (528) inFIG. 9. In the side view, the revolving valve body (518) is bone-shaped,with the front parts (530) and (532) being on the one hand in contactwith the grooved-ring seal (512) and on the other hand with the section(516) of the cartridge element (504). It is clear that the cylindricalsection (520) can be flowed around completely by the medium such aspolishing paste to be issued by the high-pressure dosing gun (500) or(600). This medium is conveyed by a compressed air motor, not shown butalready mentioned, from the housing (502) via the supply chamber (534)into the first working chamber (536) between the revolving valve body(518) and the inner face of the first casing (506).

The revolving valve body (518) is designed symmetrically both in itsmain axis (518) and in its secondary axis (540) running perpendicularthereto. The advantage thereby obtained is that when a valve head (522)or (524) is worn, the revolving valve body (518) only has to be turnedin order to align the not yet worn valve head (524) or (522)respectively to the hollow cylinder (514) forming the valve seat (542)on the front. Here, the hollow cylinder (514) is also designedsymmetrically in both its longitudinal axis (538) and its secondaryaxis, so that turning is possible.

The hollow cylinder (514) or valve seat can be of carbide, ceramics,boron carbide or similar.

The first working chamber (536) is sealed on the one hand between thevalve seat (542) and the valve head (522) contacting it, and on theother hand by the grooved ring (512) supported on the outer face of thehollow cylinder (514).

The hollow cylinder (514) is now designed movable relative to the firstcasing (506), in order to be at a distance from or in contact with thevalve head depending on the pressure prevailing in the first workingchamber (536). To do so, a second casing or bush (544) is provided thatsurrounds the first casing (506) in some areas and is designed to bemovable along this casing. The second casing (544), i.e. the hollowcylinder-shaped body, has a front section (546) that tapers outwards andin whose interior a seal (548), preferably of nylon, can be insertedthat is connected with the hollow cylinder (514) in a press fit, forexample. A nozzle (550) is in contact with the outside of the seal(548), through which the medium is sprayed. The nozzle (550) is held bya first cap nut (552) which can be screwed onto the section (546) of thesecond casing (544) in such a way that the seal (548) is clamped in thetapered extension of the internally conical section (546) of the secondcasing (544). As a result, the hollow cylinder (514) providing the valveseats (542) and (554) is fixed at the same time.

The second casing (544) has one or more leak holes (572) which preventvacuum or gauge pressure building up between the first and secondcasings (506) and (544) in the area (574) of the hollow cylinder (514)as a result of the movement of the second casing relative to the first,which might impair mutual movability. In addition, medium coming out ofthe seal (548) and passing along the outer face into the area (574) cancome out of the leak holes (572) so that medium cannot collect andthereby affect movability. At the same time it becomes clear when mediumcomes out that an inspection of the seal (512) and of the hollowcylinder (514) is necessary.

The second casing (544) can now be moved against the force of a spring(556) fixed between the second casing (544) and a second cap nut (558)extending from the cartridge element (504). The force of the spring(556) is directed such that the second casing (544) is forced in thedirection of the housing (502). As a result, contact of the valve seat(542) with the valve head (522) of the revolving valve body (518)arranged fixedly in the cartridge element (504) and hence in the housing(502) is achieved.

The front part of the second cap nut (558) has a section (560)projecting radially inwards that serves as a stop for the second casing(544).

Movement of the second casing (544) and hence liftoff of the valve seat(542) from the valve head (522) takes place when the pressure prevailingin the first working chamber (536) overcomes the force exerted by thespring element (556). In this case, the medium can flow through achannel (562) extending into the nozzle (550) to be sprayed.

In order to turn round or replace the wear parts such as the revolvingvalve (518) and the hollow cylinder (514) containing the valve seats(542) and (554), it is only necessary to remove the second cap nut (558)after loosening the first cap nut (552), so that the second casing (544)and then the first casing (506) can be removed one after the other forsubsequent changing or turning of the wear parts.

The embodiment according to FIG. 6 differs from that in FIG. 5 to theextent that lifting off of the second casing (544) and hence of thevalve seat (542) from the valve body (518) is with the assistance ofcompressed air, with mixing of the spray medium and compressed airtaking place simultaneously by outlet channels (562) running in the areaof the nozzle (550).

A second working chamber (564) connected to a compressed air source notshown is provided for this purpose.

The second working chamber (564) is laterally limited on the one hand bythe section (508) extending radially outwards of the first casing (506)and on the other hand by a section (566) parallel thereto and extendingradially outwards of the second casing (546), whose opposite wall servesas a support for the spring element (556). The second working chamber(564) is further limited by a section of the inner wall of the cap nut(558) and by the outer face of the first casing (506) or an annularelement not shown in detail.

If the working chamber (564) is acted upon by to compressed air, part ofthe spring force exerted by the spring element (556) is overcome. As aresult, liftoff of the valve seat (542) from the valve head (522) isassisted. The compressed air then flows from the working chamber (564)through the area between the second casing (544) and the second cap nut(558) to the outlet channels (562).

I claim:
 1. In a dosing gun for spraying a medium such as polishingpaste comprising a housing, a cartridge element held in said housing, avalve body, a valve seat, a spring element, means defining a firstworking chamber between said valve seat and said valve body, said valvebody and said valve seat being movable relative to one another againstthe force of said spring element if an adequate pressure is generated bysaid medium in said first working chamber between said valve seat andsaid valve body, and a nozzle;the improvement comprising a first casing,said valve body being mounted detachably on said first casing, saidfirst casing extending from one of said cartridge element and saidhousing, means defining a hollow cylinder movable relative to said firstcasing, said valve seat being formed in the frontal part of said hollowcylinder, and a second casing operatively connected to said meansdefining a hollow cylinder and movable against said spring element.
 2. Adosing gun as set forth in claim 1 including a cap nut securing saidnozzle to said dosing gun.
 3. A dosing gun as set forth in claim 1including means defining outlet channels for supplying air in the areaaround said nozzle, and means for supplying air under pressure to saidoutlet channels.
 4. A dosing gun as set forth in claim 1 in which thereis a space around the valve body through which said medium can flow, andsaid valve body is spaced from said first casing by spacer elementswhich extend integrally from said valve body.
 5. A dosing gun as setforth in claim 4 in which the valve body and its spacer elements aresymmetrical with regard to a primary axis extending through the centerof said valve body, towards said nozzle and to a secondary axis,perpendicular thereto.
 6. A dosing gun as set forth in claim 1 in whichthe hollow cylinder is symmetrical with regard to a primary axisextending through the center of said hollow cylinder and towards saidnozzle, and to a secondary axis, perpendicular thereto.
 7. A dosing gunas set forth in claim 1 including means defining outlet channels forsupplying air in the area around said nozzle, means for supplying airunder pressure to said outlet channels extending radially outwards fromsaid first and second casings, means defining a second working chambersuch that, when acted upon by compressed air, said second casing ismovable against the force of the spring element, with a connectionexisting between said working chamber and said outlet channels.
 8. Adosing gun as set forth in claim 1 in which said first working chamberis sealed.
 9. A dosing gun as set forth in claim 8 in which said firstworking chamber is sealed by a grooved ring on the outside of the hollowcylinder.
 10. A dosing gun as set forth in claim 1 including a seal,between the hollow cylinder and the nozzle and supported on the secondcasing, and a cap nut holding said nozzle, said nozzle being threadablyconnected to said second casing for fixing of said cap nut and saidseal.
 11. A dosing gun as set forth in claim 10 in which said seal incomprised of plastic.
 12. A dosing gun as set forth in claim 1 includinga second cap nut surrounding said casing in some areas and extendingfrom the cartridge element or the housing, the spring element runningbetween the outside of the second casing and said second cap nut.
 13. Adosing gun as set forth in claim 12 in which the second cap nut has astop limiting the movement of the second casing.
 14. A dosing gun forspraying a medium such as polishing paste comprising a housing, acartridge element held in said housing, a valve body in said housing, aspring element, said valve body being movable against the force of saidspring element, a valve seat, said valve body being at a distance fromor in contact with said valve seat, a nozzle and a first cap nut holdingsaid nozzle, said nozzle having a contact collar in contact on theinside with said first cap nut;the improvement in which said nozzle isheld by said first cap nut so as to be rotatable and axially movableagainst the force of said spring element.
 15. A high-pressure dosing gunas set forth in claim 14 including a perforated disk element containingsaid valve seat, said perforated disk element being in floating contactwith said nozzle.
 16. A high-pressure dosing gun as set forth in claim15 including a further cap nut threadably connected to said cartridgeelement and fastening said first cap nut, said further cap nut having afront passage orifice which has, at least in some areas, a lower cleardiameter than the perforated disk element.
 17. A high-pressure dosinggun as set forth in claim 14 including a first wall and a second,movable wall, said spring element being supported, on the one hand,against said first wall and, on the other hand, against said second,movable wall, and said valve body being operatively connected to a valvepiston, said second movable wall being movable into contact with therear face of said valve piston.
 18. A high-pressure dosing gun as setforth in claim 17 including a valve piston guide in which said valvebody is movably mounted, said valve piston guide having a section with ashoulder used as a stop for the second wall.
 19. A high-pressure dosinggun as set forth in claim 18 in which said section used as a stop is areplaceable wear bush.
 20. A high-pressure dosing gun as set forth inclaim 19 in which said valve body is a hollow element through which saidmedium flows, and including a continuous seal in the walls of saidhollow element to seal against said wear bush.
 21. In a dosing gun forspraying a medium such as a polishing paste comprising a housing, acartridge element extending from the housing, a spring element, a valvebody and an associated valve seat, means defining a first workingchamber between said valve seat and said valve body, said valve body andsaid valve seat being movable relative to one another against the forceof said spring element if an adequate pressure is generated by saidmedium in said first working chamber, and a nozzle,the improvement inwhich said dosing gun further comprises a hollow guide cylindersurrounding at least some areas of said valve body, said valve body andsaid hollow guide cylinder being movable relative to one another, avalve element which includes said valve seat, said valve element beingpositioned between said hollow guide cylinder and said nozzle, meansdefining a further working chamber, and means for supplying compressedair to said further working chamber to move said valve body relative tosaid valve element.
 22. A dosing gun as set forth in claim 21 includinga cap nut securing said nozzle to said dosing gun.
 23. A dosing gun asset forth in claim 21 including means defining outlet channels forsupplying air in the area around said nozzle, and means for supplyingair under pressure to said outlet channels.
 24. A dosing gun as setforth in claim 21 in which said valve body is a hollow needle having aradially curved outlet channel at its end section projecting into saidfirst working chamber and said valve body comprising a valve headsupported on the end of said hollow needle in said first workingchamber.
 25. A dosing gun as set forth in claim 21 in which said valvebody includes an element extending radially outwards which isconstructed and arranged so that, on one side, it faces and closes saidfurther working chamber and, on the opposite side, it is acted upon bysaid spring element with a force directed away from the housing.
 26. Adosing gun as set forth in claim 25 in which said radially-extendingelement is a piston.
 27. A dosing gun as set forth in claim 25 in whichsaid valve body surrounds a hollow cylinder in axially movable manner,said cylinder being connected to the housing or the cartridge elementand providing a passageway for said medium to be sprayed by said dosinggun.
 28. A dosing gun according to claim 21 in which the nozzle issupported by said hollow guide cylinder and has an insert of carbide toprovide a valve outlet orifice on its outside and said valve set on itsinside.
 29. A dosing gun as set forth in claim 28 in which the valveseat is flat to make contact with a flat front face or a flat or ifnecessary elastic replaceable end piece of the valve body.
 30. A dosinggun as set forth in claim 21 including a line carrying the medium and acheck valve in said line, said valve comprising a replaceable unitincluding a screw-in cage, a contact spring therein, a valve ball, avalve seat and sealing disc.
 31. A dosing gun as set forth in claim 21in which the first working chamber contains said medium and said firstworking chamber is sealed by, on the one hand, said valve seat and, onthe other hand, by a seal running between the valve body and the hollowguide cylinder.